Process gases containing sulfur dioxide, SO2, are generated in many industrial processes. One such industrial process is the combustion of a fuel, such as coal, oil, peat, waste, or the like in a combustion plant, such as a power plant. In such a power plant, a hot process gas, often referred to as a flue gas, is generated containing pollutants including acid gases, such as sulfur dioxide, SO2. Removal of as much of the acid gases as possible from the flue gas is necessary before the flue gas may be released to the atmosphere or ambient air. Another example of an industrial process in which a process gas containing pollutants is generated is the electrolytic production of aluminum from alumina. In that process, flue gas containing sulfur dioxide, SO2, is generated within venting hoods of electrolytic cells.
WO 2008/105212 discloses a boiler system comprising a boiler, a steam turbine system, and a seawater scrubber. The boiler generates, by combustion of a fuel, high-pressure steam utilized in the steam turbine system for generating electric power. Seawater is collected from the ocean, and is utilized as a cooling medium in a condenser of the steam turbine system. The seawater is then utilized in the seawater scrubber for absorbing sulfur dioxide, SO2, from flue gas generated in the boiler. Sulfur dioxide, SO2, is absorbed in the seawater and forms sulfite and/or bisulfite ions. Effluent seawater from the seawater scrubber is forwarded to an aeration pond. Air is bubbled through the effluent seawater in the aeration pond for oxidation of the sulfite and/or bisulfite ions to sulfate ions for release back to the ocean together with the effluent seawater. The sulfite and/or bisulfite ions are oxidized in the aeration pond to sulfate ions by means of oxygen gas contained in the air bubbled through the effluent seawater.
EP 2578544 A1 discloses a seawater oxidation basin system for treating effluent seawater. The disclosed oxidation basin system includes a first supply pipe for distributing an oxidation enhancing substance in the effluent seawater, a second supply pipe for distributing an oxidation enhancing substance in the effluent seawater, and a control device for controlling a first amount of oxidation enhancing substance supplied by one of the first and second supply pipes independently from a second amount of oxidation enhancing substance supplied by the other one of the first and second supply pipes.
JP 2012/115764 A discloses a seawater flue gas desulfurization system comprising a flue gas desulfurization tower in which a flue gas is brought into gas-liquid contact with seawater to carry out a desulfurization reaction of sulfur dioxide (SO2) to sulfurous acid (H2SO3). A diluting mixing tank is provided at a lower side of the flue gas desulfurization absorption tower for mixing of sulfur-containing used seawater with fresh seawater for dilution of the sulfur-containing used seawater. Further, an oxidation tank is provided on a downstream side of the diluting mixing tank equipped with an aeration apparatus for carrying out water quality recovery treatment of the seawater used for dilution, and a wastewater channel. The wastewater channel has multiple steps of partition walls, the height of which are made to be successively lower from an upstream side to a downstream side.
WO 2013/146143 A1 discloses a seawater desulfurization and oxidation treatment device including an oxidation/aeration tank for performing water quality restoration treatment on acid desulfurization seawater containing sulfurous acid (H2SO3). This acid desulfurization seawater is generated by subjecting exhaust gas from a boiler to seawater desulfurization, using dilution seawater and air. The oxidation/aeration tank is configured comprising a main flow path having an upstream-side weir formed on the inlet side in the longitudinal direction of the oxidation/aeration tank into which the dilution seawater is introduced. The oxidation/aeration tank also includes an upstream-side mixing portion formed on the upstream side from the upstream-side weir for mixing the acid desulfurization seawater with the dilution water while introducing the acid desulfurization seawater therein. A sub flow path supplies the dilution water detoured from the upstream—side mixing portion of the oxidation/aeration tank, to post-dilute the acid desulfurization seawater oxidized and aerated in the oxidation aeration tank.
The above background art illustrates the fact that generally seawater treatment plant designs provide for flat bottomed basins/ponds equipped with air blowers for maintaining oxidation air, and a weir downstream of the aeration basin followed by a discharge basin/pond/channel. Further, seawater treatment basins are in general designed to have two different zones: a mixing zone for the mixing of absorber effluent seawater and fresh seawater for dilution; and an aeration zone equipped with air blowers for seawater sulfite oxidation. In the interest of reducing capital expenses and operational expenses associated with seawater treatment plants, new methods and systems for treating effluent seawater are needed.